Modeling the kinetics of cell enlargement of Larix gmelinii Rupr (Rupr) in Central Siberia

<p>Trees are a kind of natural archives of information about the environment. The internal factors of cell growth and maturation in combination with external conditions code the tree-ring structure of conifers. The process-based models of tree-ring growth contribute to better understanding of the link between environment, wood formation and structure and allow projecting further growth. In this study we apply the VS-model to model and analyse the intra-annual cell anatomy of <em>Larix gmelinii</em> Rupr (Rupr) growing in continuous permafrost zone of Central Siberia. Anatomical measurements obtained between 1950 and 2011 have demonstrated the low number of cells determining low tree-ring growth is due to the challenging climatic conditions of the permafrost zone. The parameterization of the VS-model provided highly significant positive correlations between simulated growth curves and initial tree-ring chronology (R = 0.65). The results of timing procedure show that VS-model makes it possible to link climate and the tree-ring structure. The procedure revealed strong relationships between modelled growth rates and measured tracheid radial sizes for the full period 1950 - 2011. Seasonal observations of the number of cells during the season allow some important comparisons to be made. The results of timing procedure the growth rates modeled for the 2011 growing season fit well the timing (R = 0.91) and the observed number of cambial and enlarging cells (R = 0.78 and 0.87, respectively). Moreover the comparision the number of days from the start of the growth season to when the first cell moved into the enlargement zone with the average growth rates during this period showed that years with low growth rates at the beginning of the growing season correspond to continuous lags in the cells escape from the cambial zone. Using a novel approach of timing of cell enlargement the number of enlarging cells modeled for the 2011 growing season was well matched with the number of enlarging cells observed on micro-cores collected in the field. However, the model was unsuccessful in accurately determining the end of the growing season, overestimating the season by a several weeks. This study has shown that the VS model successfully simulates xylogenesis for larch growing in the permafrost zone both in case of “average tree” and for individual plants. Even at the individual tree level, this approach to modelling intra-annual dynamics has great potential for studying how climate affects tree-ring growth and formation.</p><p>This work was supported by the Russian Ministry of Science and Higher Education (project  #FSRZ-2020-0010) and the Russian Science Foundation (Grant 18-14-00072 P).</p>